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VBNET:ScriptingisthepastPart1
How to: Scripting is the past Native code is the future! Author: Created by: X Web: http://www.createdbyx.com/ Date: December 2, 2004 The code is written in vb.net and demonstrates how an application can compile actual fully featured vb.net code and create/call the objects and methods that are in that code. The code that gets compiled is not being parsed as it is running it really is being compiled to native code no differently than had you written and compiled the code your self using the vb.net IDE. Simply create a new console application in vb.net and copy/paste the code below into the code window to run. The code is pretty self explanatory and easy enough to read through and understand. I hope this example app helps to inspire developers out there. 'Created by: X 'Web: http://www.createdbyx.com/ 'Date: January 28, 2004 ' Public Module General Public Sub Main() Dim Assm As System.Reflection.Assembly Dim Source As String Dim GenClass As Boolean = True ' change this to False to see different output ' build script code. Normally this would be done by loading a file containing the script code. Console.Write("Building script ...") Source = BuildScript(GenClass) Console.Write(" Done.") Console.WriteLine() ' now compile the script using codedom Console.Write("Compiling script ...") Assm = CompileScript(Source) If Not Assm Is Nothing Then Console.Write(" Done.") Console.WriteLine() Console.WriteLine("Running script ...") Console.WriteLine("---------------------------------------------------------") If GenClass Then Dim Obj As Object = Assm.CreateInstance("Test", True) ' we create the obj rather than getting it's type reference Dim Meth As Reflection.MethodInfo = Obj.GetType.GetMethod("TestIt") 'NOTE: You may need to specfy the owner of the method if the method is not declared shared. ' For example if System.Console.WriteLine was not a shared member you would need to ' specify Meth.Invoke(obj, Nothing). For example this code will cause an error ' Meth.Invoke(New CodeDom.CodeExpression(), Nothing) because the method does not belong to ' CodeDom.CodeExpression it belongs to Obj. Meth.Invoke(obj, Nothing) Else Dim Obj As Type = Assm.GetType("Test") ' get type reference for module Dim Meth As Reflection.MethodInfo = Obj.GetMethod("TestIt") 'NOTE: You may need to specfy the owner of the method if the method is not declared shared. ' For example if System.Console.WriteLine was not a shared member you would need to ' specify Meth.Invoke(obj, Nothing) Meth.Invoke(Nothing, Nothing) End If End If Console.WriteLine() Console.WriteLine("---------------------------------------------------------") Console.WriteLine("Press enter to quit...") Console.ReadLine() End Sub Public Function BuildScript(Optional ByVal GenerateClass As Boolean = True) As String Dim Source As String If GenerateClass Then Source = "Public Class Test" & vbCrLf Source &= "Public Sub TestIt()" & vbCrLf Source &= "System.Console.WriteLine(""Class code Worked!"")" & vbCrLf Source &= "End Sub" & vbCrLf Source &= "End Class" Else Source = "Public Module Test" & vbCrLf Source &= "Public Sub TestIt()" & vbCrLf Source &= "System.Console.WriteLine(""Module Code Worked!"")" & vbCrLf Source &= "End Sub" & vbCrLf Source &= "End Module" End If Return Source End Function Public Function CompileScript(ByVal Source As String) As Reflection.Assembly Dim CodeP As New Microsoft.VisualBasic.VBCodeProvider() Dim Com As CodeDom.Compiler.ICodeCompiler Dim Param As New CodeDom.Compiler.CompilerParameters() Dim Ret As CodeDom.Compiler.CompilerResults ' we do not want to generate a file Param.GenerateExecutable = False ' get a reference to the compiler Com = CodeP.CreateCompiler() ' Add the System.dll assembly so that the compiled script can write out to the console. Param.ReferencedAssemblies.Add("System.dll") ' Nopw we compile the script. Ret = Com.CompileAssemblyFromSource(Param, Source) ' If there were errors during compile tell user. If Ret.Errors.HasErrors Then Console.WriteLine() Console.WriteLine() Console.WriteLine(Ret.Errors.Item(0).ErrorText) Return Nothing End If ' Return the compiled assembly. Return Ret.CompiledAssembly End Function End Module